More than 50,000 Britons have quit their jobs to care for relatives with dementia, according to landmark research which discloses that the condition is now costing businesses £1.6bn a year.

Jeremy Hunt, the Health Secretary, last night warned that the “fabric of society” is under attack from the condition, with too many carers being forced out of work prematurely because employers and local communities offer them insufficient support.

The research by Public Health England shows that one in eight people are now looking after someone with dementia, with more than half attempting to “juggle” paid work with caring duties.

It comes ahead of a major TV advertising campaign to encourage members of the public to sign up as “dementia friends,” who will receive advice about how to support those with the condition.

The scheme, launched by David Cameron, aims to ensure that businesses, individuals and communities respond better to the needs of those with dementia and their loved ones, to ensure they are left less isolated.

Official figures suggest that almost 700,000 people in England suffer from the condition - a figure which is forecast to double within 30 years, amid a rapidly-ageing population.

The report by the Centre for Economics and Business Research is the first to examine the economic impact of conditions such as Alzheimer’s disease on business and employment practices across the country.

It found that 550,000 individuals in England are now caring for someone with dementia.

Just over half such carers are also holding down paid jobs, the research shows - on average, carrying out 18 hours’ caring duties on top of their employment, the study found.

But 50,000 carers in England alone were forced to quit their jobs, as the dual burden became too great, the report found.

A further 66,000 made significant adjustments to their work - such as reduced hours - in order to care for their loved ones.

The report found that every year, the hours lost to caring commitments equate to £1.6bn a year.

Health officials said the study found businesses from a range of sectors said they were keen to do more to support those with dementia, and their carers.

However, few had yet introduced adjustments, such as flexible working hours, extended leave or access to counselling services.

Just one in ten employers said they had employed a person with dementia, with large businesses three times more likely than small firms to have done so.

The research found 33,000 people with dementia in paid work.

Last night Mr Hunt said: “Dementia isn’t just a health condition – it attacks the fabric of our society and can take a huge toll on the families and friends of those affected by the disease. I am urging everyone – families, communities and businesses to come together to ensure that people with dementia can continue to live fulfilling and rewarding lives.”

Duncan Selbie, chief executive of Public Health England, said companies should do more for vulnerable customers, by providing help with common difficulties such as paying for goods, or filling in forms.

Research among those with dementia found that help with shopping and banking were among their main priorities.

One in three people over the age of 65 will develop dementia, with risks doubling every five years.

A TV advertising campaign starting today will see 27 celebrities including the author Sir Terry Pratchett, musicians Lily Allen and Chris Martin, and presenters Fiona Phillips and Eamonn Holmes urging the public to become dementia friends.

The group will star in a music film, performing the Beatles track “With a little help from my friends” as Sir Paul McCartney is announced as an ambassador for the national campaign, led by the Alzheimer’s Society.

Later this month the charity will announce the winners of new awards, supported by The Telegraph, to celebrate efforts to create more dementia-friendly communities.

Businesses including Marks & Spencer, Argos, Homebase and Lloyds Banking Group have committed to sign up more than 400,000 staff to undergo training to support customers with the condition.

Jeremy Hughes, chief executive of Alzheimer’s Society said: “The fact that thousands of workers in this country are juggling caring responsibilities without support and understanding from their employers is frightening. We’re all beginning to talk about dementia, however, society is not yet fully supportive of people with dementia - either in the workplace or in everyday life.”